This invention relates to rotary valves for internal combustion engines. More particularly, the invention relates to a rotary valve system which includes a secondary intake port for controlling the inflow of intake gases into the rotary valve, a fuel injection system, a sealing system, a cooling and emission gas exhaust control system, and a throttle control system.
Rotary valve systems typically include one or more rotating cylinders or tubes which are mounted in the engine head and include intake and/or exhaust ports which periodically communicate with the combustion chamber as the tube rotates. Intake and exhaust gases pass through the cylindrical tube and are forced into or evacuated from the combustion chamber when the respective ports are aligned with the port of the cylinder head. Such rotary valves are believed to be superior to traditional poppet valves which have complicated drive systems including a cam shaft, lifter rods, rocker arms and springs. For example, the maximum rpm of conventional combustion engines is limited by the complicated operation of the poppet valves. In contrast, combustion engines that employ rotary valves include no such limitation and it is believed that such rotary valve engines can idle at rpms of about 400 to 600 rpm and have a high speed operation at about 10,000 to 25,000 rpm.
In addition to the improved performance of the engine, there are many other advantages of the rotary valve system over the traditional poppet systems. For example, one recognized disadvantage of traditional poppet valve systems, and prior art rotary valve systems, is that the intake mixture is subjected to at least three drastic changes of pressure. Most notably, the intake mixture achieves a high pressure behind the poppet valve when the poppet valve closes. This high pressure causes the atomized fuel particles to combine to form larger fuel particles behind the intake valve. Such larger fuel particles require significantly longer burning times and are sometimes not completely burned. This results in inefficient combustion of the intake mixture and emission problems due to the unburned fuel contained in the exhaust. Similarly, prior art rotary valves have allowed the intake mixture to develop a high pressure within the tube of the rotary valve between the periodic alignment of the intake port and the combustion chamber. When the intake port rotates into alignment with the combustion chamber, the high pressure intake mixture goes into the combustion chamber and includes large fuel particles which hinder efficient combustion and result in emission problems. Such prior art rotary valves are disclosed in, for example, U.S. Pat. Nos. 4,949,685 and 5,152,259.
Another area of recognized inefficiency in both traditional poppet valves systems and the prior art rotary valve systems is that the systems use indirect fuel injection. In particular, the fulel is injected at a fuel injection system or carburetor at the top of an intake manifold and the intake mixture must then flow through the manifold and eventually to the valving system. It is believed that it would be an improvement in the combustion engine art to provide a direct or a semi-direct fuel injection system which would directly inject the fuel into the combustion chamber. Such direct injection of the fuel results in better atomization of the fuel for more efficient combustion and less emission problems.
Most automobile engines have similar camshaft timing which does not provide for optimum operation at idle or high speeds. In such constructions, the intake valve typically opens approximately 25 degrees before top dead center and closes approximately 65 degrees after bottom dead center. Such a compromise of valve timing is a necessary sacrifice between the proper idling rpm and high rpm horsepower. As a result, performance suffers under both of these conditions. During low speed or idle operation, the intake valve closes 65 degrees after the piston passes bottom dead center. As a result, some charged air is pushed back out of the combustion chamber. Therefore, there is a requirement that a large intake manifold be provided to absorb and hold approximately 25% of this discharged air and fuel mixture until the next intake valve opening. Such a large intake manifold adds weight and cost to the vehicle.
In contrast, during high engine speed operation, by the time the intake valve closes, the pressures in the intake manifold and combustion chamber are equal, and there is no more air movement into the combustion chamber. This limits the engine rpm potential. Late intake valve closing provides higher engine rpm and creates more horsepower. However, early intake valve closing provides better idling characteristics since closing early traps more air in the combustion chamber. Under load, early intake valve closing will limit the amount of air entering the combustion chamber since there is not enough time, and the engine cannot produce enough torque or horsepower to exceed 3,000 rpm. As a result, variable camshaft timing has been introduced by some engine manufacturers in an attempt to reach the best of both conditions. However, such systems are complex, expensive and generally available only on high end automobiles. Accordingly, it is believed that it would be an improvement in the engine design field to provide a rotary valve which provides for optimum operations at both idle and high speed operation.
One obstacle which has been encountered in providing a successful rotary valve is that the rotating cylinder or tube is difficult to seal within the cylinder head. During the combustion stage, leakage of high-pressure combustion gases in the junction between the rotary valve and cylinder head can damage the surfaces of the rotary valve and cylinder head and also damage the bearing assemblies which support the rotary valve. Escape of the combustion gases also reduces the power imparted to the piston within the cylinder. During the intake phase, leakage of ambient air into the fuel/air mixture can significantly affect that mixture and severely impede the performance of the combustion engine. In addition, leakage of unburned air/fuel mixture into the exhaust gases can cause significant emission problems.
Many efforts to provide an effective sealing system for a rotary valve have concentrated on providing seals in the cylinder head around the head port which leads to the combustion chamber, such as those disclosed in U.S. Pat. Nos. 4,022,178, 4,114,639 and 4,794,895. Such seals are fixed in the cylinder head and constantly engage the same portion of the rotary valve so that lubrication has little opportunity to enter the junction between the seals and the valve. Such sealing systems are also only effective to seal one of the ports at a time when it is exactly aligned over the head port. When the ports are not aligned or are only partially aligned with the head port, they are open to the juncture between rotary valve and the valve housing and the intake and exhaust gases are free to flow along and damage the surfaces of the rotary valve and valve housing. The intake and exhaust gases also have ample opportunity to commingle and cause air/fuel mixture and emission problems.
Other sealing systems have included both a set of annular seals mounted on the valve, which seal the flow of gases in the longitudinal direction, and a set of axial seals mounted in the cylinder head and extending along the head port for sealing the port in the radial direction, such as disclosed in U.S. Pat. Nos. 4,019,487, 4,852,532 and PCT Publication WO 94/11618.
In such constructions, variations in the movement of the rotary valve within the head causes poor alignment between the annular and axial seals, resulting in leakage of hot combustion gases between the seals and along the valve and head surfaces. In addition, there is nothing to restrain leakage radially between the ports, which allows unburned air/fuel mixture to enter the exhaust gases and cause emission problems. Moreover, all of the seals are subject to significant size changes due to the varying range of temperatures encountered by the rotary valve. For example, the axial seals must be necessarily short so that they can expand between the annular seals during elevated operation temperatures. However, this undersizing of the axial seals leaves a gap between the axial and annular seals which allows commingling of intake and exhaust gases between the intake and exhaust ports. Accordingly, it would be an improvement in this art to provide an effective sealing system for a rotary valve.